Siskiwit Lake is the largest lake on Isle Royale in Lake Superior. 4,150 acres (16.8 km2) in area, the lake has cold, clear water which is relatively low in nutrients. Tributaries include the Little Siskiwit River, and the lake's outlet is the Siskiwit River which flows into Lake Superior.
Siskiwit Lake is available for fishing, with restrictions (no motorized boats, no natural bait). Lake Trout, Brook Trout, Rainbow Trout, and Yellow Perch are found in the lake. A 2004 study of toxaphene concentrations found that concentrations were lower in Siskiwit Lake trout than in Lake Superior trout, possibly due to shorter food chains and greater reliance on zooplankton or other pelagic invertebrates.
Siskiwit Lake contains several lake islands, including Eagle Nest Island, Teakettle Island, Lost…